The shape of d-glucosamineElectronic supplementary information (ESI) available: Complete list of transition frequencies measured for the three d-glucosamine conformers. See DOI: 10.1039/c4cp03593c

The bioactive amino monosaccharide d -glucosamine has been generated in the gas phase via laser ablation of d -glucosamine hydrochloride. Three cyclic α- 4 C 1 pyranose forms have been identified using Fourier transform microwave techniques. Stereoelectronic hyperconjugative forces - essentially linked with the anomeric or gauche effect - and cooperative OH O, OH N and NH O chains, extended along the entire molecule, are found to be the main factors driving the conformational behavior. The orientation of the NH 2 group within each conformer has been determined by the values of the nuclear quadrupole coupling constants. The results have been compared with those recently obtained for the archetypical d -glucose. d -glucosamine has been generated in the gas phase via laser ablation. Three cyclic α- 4 C 1 pyranose forms have been identified using Fourier transform microwave techniques.